Why return this?

  node.js, question
var Obj = function(msg){
 this.msg = msg;
 this.shout = function(){
 alert(this.msg);
 bracket
 this.waitAndShout = function(){
 var that = this;
 setTimeout(that.shout, 5000);
 //Perform the shout method above every five seconds
 bracket
 return this;
 bracket
 Obj("shouting").waitAndShout();

Because they have to be connected.

MyClass.createBuilder().setXxx(...).setYyy(...).setZzz(...).build();